This invention relates to the encapsulation of products within a gelatin shell derived from a ribbon thereof.
The encapsulation of a wide range of products in gelatin shells is long-established. The basic technique is described in U.S. Pat. No. 2,234,479, and it has of course been substantially developed since then. Nevertheless, modern encapsulation machinery still draws gelatin ribbon from two sources to a charging station where sections of gelatin strip from both ribbons are sealed around the respective contents. Encapsulation is normally accomplished using a flat or a roller dye technique. A typical roller dye technique is described in an article entitled xe2x80x9cSoft gelatin capsules: a solution to many tableting problemsxe2x80x9d published in Pharmaceutical Technology in September 1985.
Gelatin capsules are normally made using soft gelatin and in its ribbon form prior to encapsulation it is highly flexible and deformable. Gelatin may be blended with other components to vary its characteristics in different ways for different applications. However, the term xe2x80x9cgelatinxe2x80x9d is used herein to encompass a range of gelatin based compositions which are used in encapsulation processes. Because of its flexibility and deformability, which are of course important advantages of gelatin, it tends to be very mobile as it is drawn to the encapsulation station from a source, normally the drum upon which it is cast. As a consequence, the speed at which a ribbon of gelatin can be drawn to the encapsulation station is severely limited. However, we have found that if the lateral alignment of the strip can be controlled, the ribbon may be drawn significantly more quickly to the encapsulation station, with a consequential increase in production speed. The lateral alignment of the strip can be controlled by use of sensing means for monitoring the alignment, with the sensing means being coupled to a computer which receives signals therefrom, and accordingly instructs the controlling means in response to such signals. Typically, there are pre-set limits of the alignment or misalignment of the strip, and the computer may be programmed to instruct the controlling means such that lateral misalignment of the strip is restricted to within those limits.
Lateral misalignment of a gelatin strip can be corrected in accordance with the present invention by providing for one or more support rollers in the path of a strip to the encapsulation station to be capable of shifting axially relative to the path. Using an alternative technique, this correction is achieved using an applicator guide assembly including a guide roller; sensing means for monitoring lateral movement of the strip on the guide roller; a locator roller mounted for rotation about a pivotal axis; and means for pivoting the locator roller relative to the guide roller to shift strip laterally thereon. The strip will normally pass between the guide and locator rollers. In the lateral shifting or correction of the strip using either of these techniques, the flexibility and deformability of the gelatin is of considerable assistance as it enables adjustment to be accomplished without difficulty and more importantly, without shutting down the apparatus itself.
The lateral movement or position of the strip can be monitored with reference to an edge of the strip, but because the edge of a gelatin strip can be irregular, in some preferred embodiments of the invention provision is made for the application of a longitudinal line adjacent the strip edge, with sensing means monitoring the position of that line. The line can be applied by a simple roller printer, and a line can be more easily monitored by some sensing systems.
Prior to the present invention, the speed at which a gelatin ribbon could safely be drawn into an encapsulation station was significantly restricted. Typical speeds are around 2.5 cm per second; these lower speeds being essential to prevent the migration of the gelatin strip along the axial length of guidance rollers out of alignment to such an extent that the full width thereof could not be used at the encapsulation station. However, by controlling the lateral movement and alignment of the strip in its path to the encapsulation station, we have found that significantly increased speeds can be used, subject of course, to any restrictions imposed by the manner in which the strip is created, normally by casting on a drum. Speeds of 7.5 cms/sec or more are contemplated. As a consequence, production rates can also be enhanced.
The method and the apparatus of the present invention are of particular value in processes in which some form of image is applied to one or both of the gelatin strips, which image is to appear on the eventual capsules. The lateral position of the gelatin strip is of course important when an image is to applied in a particular manner. An encapsulation method and apparatus in which an image is applied to a gelatin strip is described in an International Patent Application being filed today at the British Patent Office in our name and under our agents reference EH/42029. Reference is directed to that Application.